Rotors are known in the prior art for many purposes. A typical rotor is a substantially cylindrical structure intended to be rotated about a central axis perpendicular to the plane of the cylinder. Because this rotor will be rotated in use, it is crucially important that the rotor be precisely balanced so that excessive vibration does not occur during rotation.
Accordingly, many devices are known in the prior art for detecting an inbalance in a rotor and for correcting for this inbalance. A balancing machine of this type is shown, for example, in U. S. Pat. No. 3,751,987. The present invention represents an improvement over these prior art devices. The invention is usable on two plane balancing machines as well. Then of course two planes are detected in the measuring station and two planes are corrected--one plane after the other--in the correction station
A known prior art device first determines the inbalance of a rotor by spinning the rotor and detecting a location of the inbalance with respect to a location defined as phase 0 (zero).
The phase 0 is established by writing a chalk line or imprinting a line or the like on the rotor. A light shines on the phase 0 mark while the rotor is rotated. A photodetector produces output signals indicative of the location of the mark as detected by reflections. After the rotor comes up to speed, a voltage from the photodetector which detects the phase 0 mark is discriminated, and the highest voltage is determined to be the phase 0 mark.
The area of the rotor other than the phase 0 mark, however, may also have reflective areas. For instance, dirt or the like which is adhered to the rotor may cause spurious reflections other than those reflection caused by the phase 0 mark. It is expected that these reflections will be less than the phase 0 mark, and accordingly the highest reflection is taken as the phase 0 mark.
After a steady-state rotation is established, a threshold level is set at 80% of the highest reflection, assumed to be the phase 0 mark. The inbalance is detected with respect to this phase 0 mark in ways which are known to those of ordinary skill in the art and will not be repeated here.
The rotor is then removed from the inbalance detecting station and placed on an inbalance correcting station. The information from the inbalance detecting station is used to correct the rotor on the inbalance correcting station. Specifically, this information will typically include distance (degrees) from phase 0; and an amount of material which needs to be removed from the rotor at that position. The operator at the correcting station then determines phase 0 either by the same technique as the phase 0 was detected in the inbalance detecting station, or by manually ascertaining the location of the phase 0 mark. After phase 0 is established, the operator determines the predetermined degrees from phase 0 and removes the predetermined amount of material.
However, such a structure has problems and drawbacks. First of all, since the inbalance correcting station must independently determine phase 0, it takes extra time to so determine. The detection of phase 0 is a relatively time-consuming process, as it requires either the detection of a steady peak voltage, or requires an operator to manually determine what is believed to be phase 0. Determining the distance from phase 0 is also a relatively slow determination.
The present invention is provided in recognition of these problems, and solves these problems in a new and unobvious way.